A sublime brace from Porter and a goal to captain Jason Culina were the fruits of an electric yet mature performance from Miron Bleiberg's men who could and should have scored more, in the process putting a lid on any hopes of an immediate Sydney FC revival, as United exerted confidence and dominance over a lacklustre Sky Blues.

The win puts United in third place, four points away from Adelaide United and five from league leader Brisbane, while Sydney remain a disappointing ninth, with the Sky Blues now having their work cut out for them if they're to play finals football this season.

A typically electric Adama Traore run resulted in the first goal of the evening and the first of the season for Joel Porter, as the Ivorian winger danced his way into the box and quickly flicked the ball out to Jason Culina.

The captain's cross picked Porter out perfectly although Sydney's defence seemingly stopped awaiting an offside call - but the linesman kept his flag down, Porter continued past Stephen Keller and tucked the ball past Ivan Necevski's near post.

Porter deserved no less after a sublime, pacy and creative display, and had his brace in the second half after some fantastic work from Bas van den Brink, who picked Hiro Moriyasu's pocket as Sydney pressed forward, finding Porter just outside the box.

The 31-year-old jinked past Hayden Foxe and substitute Stuart Musialik, cutting onto his favoured left foot and blasting the ball into the top left hand corner.

Despite the scoreboard, Sydney held the ball for long periods in the first half but try as they might, could not do enough to do any damage to Gold Coast's unbeaten streak, now at 10 games.